Testing For Water

This lesson covers two main tests for detecting the presence of water: using anhydrous copper II sulfate and cobalt II chloride paper. Anhydrous copper II sulfate turns from off-white to bright blue when hydrated, while cobalt II chloride paper changes from light blue to pink. The lesson also explores the historical use of cobalt II chloride as invisible ink, which becomes visible when heated. The video concludes with a summary of these methods and their respective color changes.

What is the color change observed when anhydrous copper II sulfate becomes hydrated?

• Off-white to bright blue

• Bright blue to off-white

• Light blue to pink

• Pink to light blue

Which substance is used in the second method to test for the presence of water?

• Anhydrous copper II sulfate

• Cobalt II chloride paper

• Hydrated copper II sulfate

• Dilute aqueous solution

How does cobalt II chloride paper indicate the presence of water?

• It turns from off-white to bright blue

• It turns from light blue to pink

• It turns from bright blue to off-white

• It turns from pink to light blue

What happens to cobalt II chloride when it is used as invisible ink and heated?

• It turns light blue

• It turns blue

• It turns pink

• It becomes invisible

What are the color changes observed in the tests for water presence?

• Pink to light blue and off-white to bright blue

• Light blue to pink and bright blue to off-white

• Bright blue to off-white and pink to light blue

• Off-white to bright blue and light blue to pink